Hydrolysis and Other Reactions

Murata, K. Matsusaka, and T. Shimomura, Agric. Biot. Ghent., 1979, 43, 775. 

Okuyama, K. Hosoyama, Y. Hiraga, G, Kurono, and T. Takemoto, Chem. Pharm. Bull., 1978, 26, 3071. 

Hydrolyses of the glycosidic linkages of phenyl a- and 3-D-glucopyranoside were studied at different alkali concentrations, and the reaction rates increased rapidly above 2M. Mechanisms involving direct hydrolysis and the intermediacy of l,6-anhydro- 8-D-glucose and, with the j3-anomer, the l,2-a-anhydride were proposed. Analogous work with p-acetylphenyl 3- and 5-0-methyl- 3-D-xylo-furanoside led to the conclusion that the 2-oxyanions (and presumably 1,2-anhydrides) were involved as intermediates.  

From study of the action of invertase on derivatives of sucrose and methyl jS-D-fructofuranoside, it was concluded that small changes at positions 1, or 6 cause loss of enzymic acitivity various azido-, deoxy, and halogenated-derivatives were examined.  

Lonnberg and L, Valtonen, Finn. Chem. Lett., 1978, 209 (Chem. Abs., 1979, 90, 39 192x). 

Hydrolysis and Other Reactions. — The kinetics of the acid-catalysed hydrolysis of the conformationally rigid acetals (29) and (30) were studied as models for anomeric methyl pyranosides.  

The cleavage of sugars from the steroidal glycoside solasodine on acid hydrolysis was followed by h.p.l.c. methods, and a kinetic model was developed to describe the process.  

In the area of glycosidases, the binding constants for xylose, a series of n-alkyl jS-D-xylopyranosides and their 1-thio-analogues with the )3-D-xylosidase of B. pumilis were determined. Hydrolytic AG°, and AS° values were 

spectra of a set of xylose-based oligosaccharides are referred to in Chapter 20. 

For work on insulin-like and insulin-antagonist properties, a range of substituted phenyl and benzyl l-thio-a-D-mannopyranosides were prepared either by alkylation of the 1-thiosugar or by use of glycosylthiourea derivatives.  

Hydrolysis and Other Reactions.—Continuing earlier studies Bull. Chem. Soc. Japan, 1976, 49, 1059), Japanese workers have now examined the hydrolysis of sucrose solubilized in benzene by a reversed micelle formed from dodecyl-benzenesulphonic acid. An enhancement factor of 400 (relative to aqueous hydrochloric acid) was observed, while ethanesulphonic acid showed only slight effect. It was tentatively concluded that the enhancement is related to the formation and stability of reversed micelles. Other workers have examined the acid-catalysed hydrolysis of sucrose at different hydrochloric acid concentrations and postulate a change of mechanism at 5.68 mol 1.  

The rates of alkaline hydrolysis of 13 flavanoid glycosides were shown to be dependent on several factors including the degree of hydroxylation of the aglycones. 3,5,7,3, 4 -Pentahydroxy compounds hydrolysed more rapidly than 3,5,7,4 -tetrahydroxy- or 3,5,7,4 -tetrahydroxy-3 -methoxy analogues.  

A short review has appeared on the selective cleavage of the glucuronide 

Nishiyama, R. Adachi, and K. Nakamura, Bull. Chem. Soc. Japan, 1978, 51, 1826. 

Investigations have been made of pyridine as a reaction solvent for the 

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Cation-exchange resins are used as catalysts in the produdion of MTBE (methyl tertiary-butyl ether, 2-methoxy-2-methylpropane) and various other oxygenates and, lately, also in the dimerization of isobutene [30]. Other commercial applications of the cation-exchange resins indude dehydration of alcohols, alkylation of phenols, condensation readions, alkene hydration, purification of phenol, ester hydrolysis and other reactions [31]. The major producers of ion-exchange resins are Sybron Chemicals Incorporated [32] (Lewatit resins), Dow Chemical Company [33] (DOWEX resins), Purolite [28] (Purolite resins), and Rohm and Haas Company [27] (Amberlyst resins). 

A different type of stereoelectronic control has been found in the breakdown in solution of tetrahedral addition intermediates that arise in ester and amide hydrolysis and other reactions of carboxyl and carbonyl groups. In the case of an intermediate such as structure 8.47, in which there are two atoms with non-bonded electrons (generally O or N), the lowest-energy transition state for breakdown is a conformation in which nonbonded electrons of each are anti to the group being expelled (structures 8.48).50... 

Because of the specificity and the enantioselectivity of some enzyme-catalyzed reactions, the application of enzymes is increasingly important in asymmetric induction and kinetic resolution in organic synthesis. A large number of publications were recently reviewed, focusing on utilization of enzymes and microorganisms to stereospecific hydrolysis and other reactions to produce pure stereoisomers (2,3). However, the use of an enzyme as a catalyst has usually been limited to small-scale experiments in the laboratory. 

Esterification, hydrolysis, and other reactions of the phosphonitrilic series may often be catalyzed by pyridine and other donor molecules this effect will be considered in more detail in Section III, C, 2, d. 

Hydrolysis and Other Reactions and Features.- The pseudo first order rate constant for the hydrolysis of o-nltrophenyl 6-D-gluco-pyranoslde at pH 11.4 Increases 10 fold on addition of phenyl-boronlc acid In the presence of benzyl hexadecyl dlmethylammonlum chloride, whereas the enhancement factor for the corresponding... 

Hydrolysis and Other Reactions and Features.- A linear relationship exists between bond lengths and ease of hydrolysis for a wide range of unsymmetrical acetals, including aryl a-D-glucosldes (the C-1—0-1 bond in these cases... 

Simple Diels-Alder Additions.—The [4 + 2] and reverse-[4 + 2] cycloaddition reactions of species containing C=X bonds (X = P, As, Sb, Bi, Si, Ge, etc.) have been discussed and the evidence reviewed.The general chemical reactivities of cyclo-propenones and triafulvenes, including their behaviour in Diels-Alder reactions, have been broadly summarized. Kagi and Johnson have reported extensive studies on the Diels-Alder reactions between cyclopropene and various chloro-cyclopentadienes in which endo-adducts are obtained, selective dechlorination, hydrolysis and other reactions of these adducts, and H n.m.r. spectral correlations. 

RCHjSOjSPh ) or from thiolsulphinates with NaI04 (see also preceding sections of this Chapter). Hydrolysis and other reactions that generate sulphenic acids [RS(0)C02R + HCl CICO R + RSSR + RSO SR, " and ArSBr + OH - ArSSAr, ArSR, and RSSOj", via a thiolsulphonate see also the Sulphenic Acids section] commonly lead to thiol sulphonates. Parent salts ArSOjS M+ are readily prepared. ... 

Hydrolysis and other Reactions and Features.—A. novel method for following the add catafysed hydrolysis of sucrose and lactose involves measurement of the rate of reaction of periodate with quenched aliquot portions of the solutions using a periodate>sensitive electrode. In this way sucrose could be determined in the presence of other carbohydrates in the range 0.01-0.1 M, and the method was applied to food products. The glycosidic hydrolysis of fluorenone ketal (107), which serves as a nucleoside glycosylase enzyme model, has been shown to be intramolecularly catalysed by comparison with analogous compounds. ... 

Hydrolysis and Other Reactions and Features.- The rate limiting step in the acid-catalysed hydrolysis of alkyl a- and g-D-fructo-furanosldes has been shown to be the unimolecular heterolysis of... 

Hydrolysis and Other Reactions and Features.- The effects of substituents in the aromatic rings of 3-D-glucopyranosldes on their rates and mechanisms of hydrolysis in concentrated potassium hydroxide (12.75 M) have been studied,as have the reactions of some dlsaccharldes with alkaline hydrogen peroxide. Five different... 

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